The use of irrigation systems including pumps is described in detail in commonly-assigned U.S. Pat. No. 4,650,462. Irrigation with a fluid, typically saline solution, is provided during endoscopic procedures such as arthroscopy to distend the joint, improve viewing of the area being treated, and to remove debris which may be loosened during the procedure.
Irrigation systems such as those described in U.S. Pat. No. 4,650,462 provide substantially independent control over both flow through the area being treated and pressure of the fluid in that area. Irrigation systems which do not provide independent control over pressure and flow typically suffer from either insufficient flow to present a clear treatment site or excessive pressure which can cause other serious problems.
Irrigation systems deliver and remove fluid to the treatment site using surgical tubing. Because of biological contamination, the tubing must be replaced between procedures. Considerations regarding tubing and tubing sets used in irrigation systems are thoroughly discussed in commonly-assigned U.S. Pat. No. 4,820,265. Briefly, the tubing set must include an inflow tube to provide irrigation fluid to the treatment site and an outflow tube to remove the irrigation fluid from the treatment site. Tubing sets used with irrigation systems which monitor fluid pressure at the treatment site (such as that described in U.S. Pat. No. 4,650,462) also typically include a pressure sensing line connected between the treatment site and the irrigation system.
The pumps and tubing sets disclosed in the references discussed above use a bifurcated tubing assembly in the outflow line. One pathway of the bifurcation incorporates an outflow control section of circular cross-section which interfaces with occlusion hardware in the pump to create a fully open or fully closed valve. The valve is powered by a solenoid which pinches the outflow control tubing section against a fixed back plate. The other pathway includes a thin-walled relief section of circular cross-section which interfaces with relief hardware in the pump. The relief section is pinched by a spring-loaded plate which is designed to open the valve partially at a pressure of about 50 mmHg and fully at a pressure of about 200 mmHg. When opened, fluid passes through the relief section to reduce pressure at the irrigation site.
This arrangement has been commercially successful, but the tubeset is time-consuming and relatively complicated to load in the pump, has a higher than desirable factory cost, and wastes irrigation fluid due to the low cracking pressure of the relief section.
An additional problem with many known irrigation fluid systems including pressure sensing lines is the use of couplings in those lines which introduce errors into the pressure reading. The primary cause of the error is the use of couplings which require axial compression to provide adequate sealing between fittings. Examples of such couplings include luer-type lock fittings and other quick disconnect type fittings.